1. Field of the Invention
This invention relates to a magnetron sputtering apparatus and to a method of manufacturing a semiconductor device. In particular, this invention relates to a magnetron sputtering apparatus wherein the configuration of magnetron is desirably modified and to a method of manufacturing a semiconductor device, which includes a forming a diffusion barrier film by making use of this sputtering apparatus.
2. Description of the Related Art
The sputtering apparatus is generally constructed such that it comprises a vacuum chamber, a supply pipe connected with this vacuum chamber for feeding an inert gas such as argon, a vacuum pump connected, via an exhaust pipe, with the vacuum chamber, a combination of a substrate holder and a target which are disposed in the vacuum chamber so as to face one another, and a high-frequency power source for applying high-frequency to the substrate holder for example.
In the employment of this sputtering apparatus, a substrate is secured to the substrate holder at first and then gas is evacuated from the vacuum chamber through the actuation of a vacuum pump while feeding argon from the supply pipe to the vacuum chamber, thereby enabling the vacuum chamber to have a desired degree of vacuum. Thereafter, high-frequency is applied from the high-frequency power source to the substrate holder, thereby allowing plasma to generate between the substrate held by the substrate holder and the target. Due to the plasma thus generated, the argon is activated and caused to impinge against the target which is earthed or impressed with negative voltage, thereby sputtering the target material. The particles of target material thus sputtered are then caused to move toward the substrate and deposited on the surface of substrate, thus forming a film of target material.
This sputtering apparatus described above is accompanied with a problem that the coverage to be obtained is asymmetrical. This asymmetry may be attributed to the fact that since the neutral particles of target material (for example, metallic particles) are permitted to be sputtered preferentially from a central region of target, resulting in an increase in quantity of erosion especially at the central region of target, thereby causing the particles of target material to enter at an inclined angle into the outer peripheral portion of substrate and to deposit thereon.
With a view to minimize the asymmetry of coverage mentioned above, it has been practiced to dispose the magnetron in the vicinity of the outer periphery of the target material which is located opposite to the substrate holder, thereby increasing the quantity of erosion at the outer peripheral region of the target and hence decreasing the number of neutral metallic particles which would obliquely enter into the outer peripheral portion of substrate.
Furthermore, in the papers by B. Window and N. Savvides “J. Vac. Sci. Technol. A4(2)” 1996, p 196-202 and “J. Vac. Sci. Technol. A4(3)” 1996, p 504-508, these are disclosed measures to promote the electrolytic dissociation of neutral metallic particles to generate electrons and ions through the rotational motion of electrons along the lines of magnetic flux by making use of a divergent magnetic field, thereby attracting the electrons and ions thus generated to the substrate.
Further, JP-A 2001-140070 (KOKAI) discloses the employment of a magnetron of so-called asymmetric magnetic pole structure wherein a couple of elliptical ring-like or triangular ring-like magnets, each differing in polarity from the other, are concentrically arranged in addition to the employment of a magnetron wherein a couple of circular ring-like magnets, each differing in polarity from the other, are concentrically arranged. In this document, inner magnets are arranged to have smaller magnetic field/magnetic flux as compared with outer magnets so as to enable the magnetic field to enter into the substrate from the magnetron, thereby making it possible to create a high-density plasma region in the vicinity of the substrate.
However, this method of introducing a divergent magnetic field into the substrate by making use of asymmetric magnetic pole is accompanied with a problem that since electrons are permitted to enter into the substrate while these electrons are being entangled with the magnetic field, an electron current is generated, causing damage to the elements on the substrate.
Therefore, it is impossible, even with these arts, to concurrently overcome the problems of the suppression of aforementioned asymmetry of coverage at the sidewall and bottom of substrate and of the suppression of the aforementioned damage to the elements on the substrate.
In order to alleviate the aforementioned asymmetry, it is required to increase the quantity of sputtering from the outer peripheral portion of target and, at the same time, to enhance the degree of electrolytic dissociation of target material (for example, metal) that has been sputtered. However, according to the method of enhancing the degree of electrolytic dissociation of metal by making use of a divergent magnetic field, electrons are permitted to move along the divergent magnetic field at the time of initiating the film deposition. Because of this, the electron current is permitted to be introduced at high speed into the substrate at the time of generating plasma, thus causing damage to the elements on the substrate. For example, when a diffusion barrier film is to be formed by making use of the aforementioned magnetron sputtering apparatus subsequent to the formation of a via hole in an interlayer insulating film on the occasion of forming a via-fill for connecting an impurity diffusion layer such as source/drain regions formed on the surface of semiconductor substrate with interconnects formed on the surface of the interlayer insulating film, the asymmetry of the diffusion barrier film on the inner surface of the via hole can be alleviated. However, due to the local accumulation, through the diffusion layer, of a high-speed electron current at the gate insulating film on the occasion of depositing the film, breakdown of the withstand voltage is caused, thus badly affecting the reliability of the resultant semiconductor device.